This invention relates to a composition useful for the detection of peroxidase-like activity and in particular to the identification of peroxidase-like activity in various specimens. More particularly the invention relates to the preparation of a granular indicator material which when admixed with a separate reagent solution, is useful for the detection of peroxidase-like activity present in stool or biological fluids.
The detection of perioxidase-like activity has become an invaluable aid to the medical practitioner for the diagnosis of a number of disorders. One of the most widely used indicator reagents for diagnosing occult blood is derived from an extract from the wood of certain species of trees of the Guaiacum genus native to the American tropics. The extract, termed guaiac, turns from essentially colorless to blue in the presence of hemoglobin and an oxidizing agent such as hydrogen peroxide. More specifically, the guaiac reagent is sensitive to what is termed "peroxidase-like activity" which results from the combination of an oxidizing agent with hemoglobin or certain chemically similar compounds.
Over 100,000 persons in the United States are affected by cancer of the colon and rectum per year, occurring equally in both the male and female population. When the number of colorectal cancers occurring each year is combined with the number of cancers occurring in other digestive organs, including the esophagus and stomach, such cancers of the digestive system account for more occurrences of cancer than any other single form of the disease. Contrary to many other forms of cancer, early diagnosis and treatment of digestive tract cancer does result in a cure rate of 80% to 90% of those persons affected by the disease. If, however, the disease is not detected until the later stages, the cure rate can drop drastically to 25% or less. Thus, early detection of the disease is critical to successful treatment of digestive tract cancer.
Most, but not all, cancers of the digestive tract bleed to a certain extent. Some blood found in the gastric contents and in vomitus is indicative of conditions associated with disorders of the mucous membrane, such as ulcers, diverticulitis, colitis, and carcinoma. In contrast, some blood is deposited on and in fecal matter excreted from the digestive system. The presence of blood in fecal matter is not normally detected, however, until gross bleeding occurs, resulting in blood visible to the naked eye. Gross bleeding, however, does not normally occur until the digestive tract cancers are in advanced stages.
It is known that digestive tract cancers in the early stages also tend to bleed, giving rise to occult (hidden) blood in fecal matter. Test equipment and test procedures have been developed for use by physicians in testing for the presence of occult blood in fecal matter. One of the most successful tests is manufactured and sold by SmithKline Diagnostics of Sunnyvale, Calif., under the trademark "Hemoccult". The package for the "Hemoccult" test is disclosed in U.S. Pat. No. 3,996,006 issued to J. F. Pagano. Briefly, the Pagano test employs an absorbent white paper impregnated with a guaiac reagent encased in a special test slide having openable flaps on both sides of the test slide. To use the Pagano test slide, one must obtain a sample of fecal matter, smear it onto the guaiac-impregnated paper by opening the panel on one side of the test slide, and thereafter close the panel. A panel on the opposite side of the test slide is then opened and a developing agent, which is a stabilized solution of hydrogen peroxide and denatured alcohol, is applied to the guaiac-impregnated paper. If occult blood is present in the fecal matter smeared on the opposite side of the paper, the product of the guaiac reaction will appear as a blue substance against the white paper background, providing a positive indication of the presence of blood in the fecal matter.
Although the Pagano test is excellent for use by physicians in their offices and by diagnostic laboratories, it is not the type of test that is readily adaptable for use by the ordinary person because of his adverse reaction to handling fecal matter and because of his lack of skill in interpreting the results. As stated above, the Pagano test requires that a specimen of fecal matter be obtained. Normally, a specimen is obtained by procuring a sample on the end of a spatula or a wooden tongue depressor, which is then used to smear the specimen on the paper in the Pagano test slide. Once the sample is obtained and the test procedure completed, both the test slide and the spatula or depressor must be disposed of. Disposal of the used materials can and does present a physical problem to, if not an adverse psychological reaction for, the ordinary person. Thus, the ordinary person is not likely to use the Pagano test because of its unclean nature and because of the disposal problems associated with the used test slide and spatula or depressor. Additionally, the ordinary person does not necessarily have the skill required to analyze, and thus form accurate conclusions from the test results.
As an alternative, the ordinary person can initiate the Pagano test in his home and then forward the test slide to his physician or a laboratory for addition of the developing agent and analysis of the test. This procedure, however, requires cold storage of the test slide and specimen if there is a significant time lapse before the test can be completed. Certainly, the ordinary person does not wish to store a fecal specimen in his household refrigerator, normally the only cold storage available to him, until he can present the specimen to his physician or an appropriate laboratory. Thus, the general public is not likely to follow or comply with this alternative.
Another test for occult blood is suggested by D. E. Fonner in U.S. Pat. No. 2,838,377. The Fonner test, as disclosed, can be effected in a toilet bowl containing fecal matter. The basic test reagents employed by Fonner are o-tolidine and benzidine. These reagents in the presence of blood and other reactants produce a dye visible to the naked eye. Although the Fonner test appears to be a solution to the problem of finding a viable home test for occult blood, it has not met with success for two reasons. First, the above-listed reagents are in themselves known to cause cancer and thus are not suitable for general public distribution. More importantly, the Fonner reagents have a relatively high rate of providing false indications of the presence of occult blood as a result of tap water impurities.
Nicholls and Fonner disclose in U.S. Pat. No. 2,799,660 an occult blood test using a tablet composition containing a blood indicator, oxidizing agent, acetate compound and water-soluble solid acid. The tablet may additionally contain an effervescent agent. This test is being marketed by Ames under the trademark "Hematest". In determining the presence of absence of occult blood in a sample of urine a drop of the urine specimen is placed on a piece of dry filter paper, and when the drop has soaked into the paper a tablet prepared as above described is placed in the center of the drop and then two drops of water added to the tablet. With a positive test a ring of color appears on the filter paper surrounding the tablet, the color ranging from a very faint to a very deep blue, depending upon the concentration of blood in the sample.
To date, the use of the Pagano test, the Fonner test, and other similar tests has been limited primarily to physicians and diagnostic laboratories. Although this limitation might not at first glance present a significant problem, it does limit the early detection of digestive tract cancers, primarily because patients will not see a physician until other symptoms of digestive tract cancers, such as gross bleeding, manifest themselves. Thus, early detection of cancer of the digestive tract still does not occur with the great majority of patients who contract the disease.
While the prior art has recongnized the need for a simple and reliable test for detection of peroxidase activity, such test has not been available for routine home usage in an acceptable format.